Stationary contact structure having blow-open, blow-closed, loop current paths



Dec. 14, 1965 F. J. POKORNY ETAL 3,223,799

STATIONARY CONTACT STRUCTURE HAVING BLOW-OPEN, BLOW-CLOSED, LOOP CURRENT PATHS Filed Dec. 29. 1960 6 Sheets-Sheet 1 INVENTORS F/m'A/z J. RGA OA /VV 5044:- ,4 WA! $0M Dec. 14, 1965 STATIONARY CONTACT Filed Dec. 29, 1960 F. J. POKORNY ETAL, 3,223,799 STRUCTURE' HAVING BLOW-OPEN, BLOW-CLOSED, LOOP CURRENT PATHS 6 Sheets-Sheet z yiaqaz ,4 W4 50% Dec. 14, 1965 F. J. POKORNY ETAL 9 STATIONARY CONTACT STRUCTURE HAVING BLOW-OPEN, BLOW-CLOSED, LOOP CURRENT PATHS 6 Sheets-Sheet 3 Filed Dec. 29, 1960 H d A J $3. m A. M w t w G M fw I 7. m u L 5 w 2 7 2 V. Q o 'm\ I\ On OD 00 Q Mm w 1 r S t, y p 2 Z 7P0? Dec. 14, 1965 F. .1. POKORNY ETAL 3,223,799

STATIONARY CONTACT STRUCTURE HAVING BLOW-OPEN, BLOW-CLOSED, LOOP CURRENT PATHS 68heets-Sheet 4 Filed Dec. 29, 1960 Dec. 14, 1965 F. J. POKORNY ETAL 9 STATIONARY CONTACT STRUCTURE HAVING BLOW-OPEN, BLOWCLQSED, LOOP CURRENT PATHS 6 Sheets-Sheet 5 Filed Dec. 29, 1960 IN V EN TORS' 20? Z 4 W/(M/V BY 05 mace/v1; 16765 951% f fpppg/ D 14, 1965 F. J. POKORNY ETAL 3, 99-

STATIONARY CONTACT STRUCT URE HAVING BLOW-OPEN, BLOW-CLOSED, LOOP CURRENT PATHS Filed Dec. 29, 1960 6 Shets$heet e United States Patent STATIONARY CONTACT STRUCTURE HAVING BLOW-OPEN, BLOW-CLOSED, LOOP CURRENT PATHS Frank J. Pokorny, Hatboro, and George A. Wilson,

Media, 12a assignors t0 I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Dec. 29, 1960, Ser. No. 79,425 6 Claims. (Cl. 20087) This invention relates to circuit breakers and more particularly, to circuit breakers in which the movable arm has no movable elements mounted thereto and the stationary contact structure has semi-movable elements mounted thereto.

Circuit breakers have been designed to form a loop current path through the breaker during automatic opening operation to urge the cooperating contacts toward a disengaged position. The operation is such that short circuit current flowing through the loop sets up a magnetic field which aids the opening mechanism in operating the movable arm to its trip position. This is known as the blowopen effect.

It is also desirable during the closing operation of the circuit breaker to obtain a blow-closed effect whereby the current flowing through a loop current path in the circuit breaker sets up a magnetic field which aids the closing operation of the circuit breaker in cases where the circuit breaker is closed during excessive current conditions and further aids in providing a rigid engagement of the breaker contacts while the circuit breaker is in a closed position.

One method of producing this result is set forth in United States Patent No. 2,601,482, issued June 24, 1952, to J. D. Wood, entitled Circuit Breaker Blow-Open, Blow-Closed Contacts, and assigned to the assignee of the instant application.

In this invention, we provide a movable arm having no movable contact members mounted thereon. Movable contact members are mounted, however, on the stationary contact structure. At the instant that the cooperating contacts of the fixed structure and movable arm become engaged, the current flowing through the circuit breaker causes a blow-on effect which urges the cooperating contacts into firm engagement to effect complete closure.

During tripping operation in response to overload or short circuit conditions occurring in the controlled circuit, the current path between the movable arm and stationary contact structure generates electromagnetic forces which aid in the disengagement of the contacts.

During extreme overload or short circuit conditions, the U-shaped configurations of the studs and contacts of most circuit breakers generate extremely large electromagnetic forces.

Circuit breakers must be designed so that they will withstand such large forces even after repeated use. Also, circuit breakers must be able to operate rapidly in order to isolate the load which they protect to prevent the load from being damaged by high magnitude short circuit currents. Repeated high speed operation of this nature has a harmful Wearing effect upon the linking members which are used to pivotally mount the moving parts. This requires worn linking members to be replaced rather frequently in order to insure that safe tolerances between moving parts are maintained. The weight of all moving parts must be kept to a minimum in order to maximize their speed of operation. All of these features must be embodied into the circuit breaker without sacrificing reliability. That is, the circuit breaker must be designed to have a small number of moving parts in order to avoid any possibility of breaking down during operation.

We have solved the above problems by providing a novel circuit breaker in which the movable arm has no moving parts mounted thereto. This permits the movable arm to be made extremely strong and rigid and, at the same time, light in Weight. The decrease in Weight and the absence of moving parts enables the moving arm to be closed and opened very rapidly. The stationary terminal, which the movable arm closes upon, contains pivotally mounted contacts which cooperate with contacts mounted on the movable arm. The contact members carried by the stationary terminal are mounted so as to create a blow-on effect between the contacts of the stationary terminal and the movable arm when the breaker is in a closed position and to create a blow-off effect during the tripping operation.

The number of moving members have been reduced to a minimum and the pivotal means by which the movable members are mounted are designed so that they do not diminish the cont-act pressure when the breaker is in the closed position. The conducting supports for the pivotally mounted contact members are shaped to cause the current to follow a curved path to encourage the blowclosed effect. which provides a loop current path between the movable arm and the stationary terminal which has a larger radius than the radii of the loop current paths which exist within the stationary terminal. This causes the blow-closed forces exerted by the movable cont-act members to be much greater than the blow-open force exerted between the movable arm and the stationary terminal, thus ensuring firm contact engagement when the circuit breaker is in the closed position.

It is thus an object of our invention to utilize short circuit or overload current to aid in the tripping of the circuit breakers.

Another object of our invention is to utilize normal current flow to create a blow-off effect to aid in the open ing of the circuit breaker.

Another object of the invention is to utilize normal current flow to keep the contacts of the circuit breaker in firm engagement.

A further object of our invention is to provide a circuit breaker with a lightweight movable arm which has no moving parts mounted upon it.

A still further object of our invention is to provide a circuit breaker which is designed to have a loop current path to generate a blow-on force and a loop current path to generate a blow-off force whereby the blow-on force is greater than the blow-off force when the circuit breaker is in the closed position.

Another object of our invention is to so arrange the movable contacts that the wearing of parts after repeated use will not imp-air the effectiveness of the circuit breaker.

Still another object of our invention is to provide a circuit breaker with conducting supports which are slit in such a way as to force the current flowing through the circuit breaker to follow a curved path which encourages a blow-on effect.

The foregoing and many other objects of our invention will become apparent in the following description and drawings in which:

FIGURE 1 is a perspective view of one embodiment of the circuit breaker.

FIGURE 2 is a perspective view of the circuit breaker of FIGURE 1 with the front conductive side plate removed.

FIGURE 3 is a perspective view of the side plate removed from FIGURE 2.

FIGURES 4, 5 and 6 are side plan views of the novel circuit breaker in the closed, partially open and fully opened positions respectively.

The movable arm has a configuration.

FIGURE 7 is a cross-sectional view of the arcing contact pivot mounting taken along line AA of FIGURE 6.

FIGURES 8 and 9 show another embodiment of the contact structure of FIGURE 1.

Referring now to the figures, we have shown here a novel circuit breaker 10 which is so arranged that in the closing movement with the contacts touching, but not fully engaged, the current loops through the circuit breaker will provide blow-closed effects. When the circuit breaker is tripped the circuit breaker is so arranged to provide a blow-open effect.

The circuit breaker 10 of FIGURE 1 is shown supported by electrical terminals such as the disconnect devices and 16 mounted to support 11. Portions of disconnect devices 15 and 16 which are located on the circuit breaker side of support 11 are considered to be first ends, while portions on the other side of support 11 are considered second ends. The conductive leads 13 and 14 of the circuit to be protected are slidably mounted within the upper 15 and lower 16 disconnect devices respectively. Disconnect devices 15 and 16 are cylindrically shaped and have a plurality of fingers 17 at their ends. Circular springs 18 draw the fingers 17 inwardly to clamp conductors 13 and 14 rigidly within disconnect devices 15 and 16. Lower disconnect device 16 is connected to bridge 19 at one end thereof by pivot 20 while upper disconnect device 15 is connected to main generally L-shaped contact members 21 (having contact surfaces 36) by conductive head 40 (see FIGURE 2) and to arcing contacts 22 by conductive head 40 and side plates 25. For the sake of this analysis, conductive head 40 and side plates may be considered as part of the upper electrical terminal formed by disconnect device 15. Upper 15 and lower 16 disconnect devices are insulated from support 11 and from one another by any suitable means. Arcing contact members 22 engage butt contacts 24 and main contact members 21 engage butt contacts 23 when the circuit breaker is in the closed position. Bridge 19 is formed of a conductive material which serves as the current path between cooperating contact pairs 2224, 21-23, and pivot 20, where pivot 20 serves as the electrical connection between bridge 19 and disconnect device 16. It is noted that butt contacts 23 and 24 are fixedly mounted a fixed distance apart on a second end of bridge 19. Side plates 25 are secured to the conductive head 40 (see FIGURE 2). They serve as the support means for arcing contacts 22. Pushrod 45 serves to operate bridge 19 between its open and closed positions. The current loops between disconnect device 15 and main 21 and arcing 22 contacts generate blowclosed effects as will be more fully described.

FIGURE 2 shows the circuit breaker 10 with the front side plate 25 removed. Conductive head 40 is secured to the extension of upper disconnect device 15 and is suitably insulated from support 11. The upper end 31 of conductive head 40 serves as the mechanical and electrical connection between the circuit breaker 10 and an arc chute which may be pivotally mounted thereto. A description of this pivotal mounting is set forth in copending US. application Serial No. 77,433, entitled Mechanical and Electrical Pivot Between Removable Arc Chute and Stationary Contact Structure filed December 21, 1960 in the name of Frank J. Pokorny and assigned to the same assignee as the instant application.

Rear side plate 25 is bolted to conductive head 40 by means of holes 32 and 33 which extend through conductive head 40. The underside of conductive head 40 has a groove 38 in which is inserted a first end of main contact member 21. A U-shaped bracket 28 is inserted between side plates 25 by means of a slot (see FIG- URE 6) in each side plate 25. Groove 34 in main contact member 21 serves as a seating means for spring 29, the other end of which is seated within bracket 28. Spring 29 urges the lower end of main contact 21 into engagement with butt-contacts 23 when bridge 19 is in the position as shown in FIGURE 2. Both main contacts 21 are mounted in this manner. Arcing contacts 22 are mounted to side plates 25 by pivot 26. Springs 37 which are seated between groove 38a of conductive head 40 and the cone-shaped holes 39 of arcing contacts 22 (see FIGURE 4), urge arcing contacts 22 clockwise around pivot 26 into engagement with butt contacts 24 when bridge 19 is in the position shown in FIGURE 2. Stop pin 41, mounted between side plates 25 restrains the clockwise movement of arcing contacts 22 and the counterclockwise movement of main contacts 21 when bridge 19 is moved clockwise by pushrod 45 around pivot 20, which operation will be subsequently described. The current path through main contacts 21 is shown by phantom line 50. It can be seen that a loop current path 51 is formed directly behind main contacts 21. During normal operation current loop 51 generates a magnetic field which is crowded between conductive head 40 and main contact 21 in the region designated by numeral 42. This magnetic field causes a blow-on eifect which urges main contacts 21 counter-clockwise around point 35 and into firm engagement with butt contacts 23. The radius of loop 51 is much smaller than the radius of loop current path 52 (formed between butt contact 23 and bridge 19) so that the blow-closed effect generated by loop 51 is much greater than the blow-open effect generated by loop 52.

FIGURE 3 is a perspective view of front side Plate 25. Main 21 and arcing 22 contacts are shown in the position they occupy when bridge 19 is in the closed position (see FIGURE 2). U-shaped bracket 23 (see FIGURE 2) protrudes through slot 60 in side plate 25 which slot secures and positions bracket 28 in order that spring 29 may be properly seated behind main contact 21. Stop pin 41 (see FIGURE 2) is secured to side plate 25 by means of bolt 56. Solid phantom line 53 shows the current path between conducting head 40 (shown by the broken line) side plate 25, pivot 26, arcing contact 22 and butt contact 24. The loop 54 of current path 53 generates a blow-closed eflect which urges arcing contact 22 clockwise around pivot 26 into firm engagement with butt contact 24. The radius of current loop 54 is much smaller than the radius of current loop 52 (see FIGURE 2) so that the blow-closed effect of loop 54 is much greater than the blow-open elfect of current loop 52.

Side plate 25 has a notch 55 which serves to channel the current immediately behind arcing contact 22 in order to form loop current path 54. Arcing contact 22 is electrically connected to side plate 25 by pivot 26. The coneshaped insulating caps 58 (see FIGURE 4) seated between spring 37 and the conical bore 39 in arcing contacts 22 prevent current from flowing between arcing contact 22 and conductive head 40 through springs 37. Thus, caps 38, 58 cause all the current flowing through arcing contact 22 to follow current path 53. The electrical connection between side plates 25 and arcing contacts 22 will be fully understood in connection with the description of FIGURE 7.

The tripping operation of circuit breaker 10 in connection with FIGURES 4 through 7, is as follows: During normal current flow, the closed position of circuit breaker 10 is as shown in FIGURE 4. Each arcing contact 22 is urged into engagement with its associated butt contact 24 through the combined actions of blow-on loop current path 54 and its associated spring 37. Each main contact 21 is urged into engagement with its associated butt contact 23 through the combined actions of blow-on loop current path 51 and associated spring 29. Bridge 19 is rigidly held in the closed position by pushrod 45, which is controlled by any well known actuating means (not shown).

On the occurrence of a fault current, the pushrod actuating means (not shown) will be energized causing pushrod 45 to move bridge 19 clockwise about pivot 20. Springs 29 and 37 and blow-closed loop current paths 51 and 54 normally function to urge main 21 and arcing 22 contacts, respectively, into engagement with their cooperating butt contacts 23 and 24. However, during the tripping operation springs 29 and 37 and blow-closed loop current paths 51 and 54 aid in the opening of bridge 19 by helping to rotate bridge 19 clockwise at a more rapid rate.

As bridge 19 moves in a clockwise direction arcing contacts 22 move clockwise about pivot 26, keeping arcing contacts 22 in continuous engagement with butt contacts 24. Simultaneously therewith, main contacts 21 move counterclockwise about contact point 35, keeping main contacts 21 in continuous engagement with cooperating butt contacts 23. After having traversed an arc of predetermined length, main contacts 21 are restrained from any further counter-clockwise movement by stop pin 41. This can best be seen in FIGURE 5. Main contacts 21 thereupon become disengaged from butt contacts 23. However, arcing contacts 22 remain in engagement with butt contacts 24 thereby channeling the current flow between conductive head 40 and bridge 19 to arcing 22 and butt 24 contacts which are still in engagement (see FIGURE 5).

As bridge 19 moves still further in the clockwise direction, arcing contacts 22 rotate clockwise about pivot 26 to the position shown in FIGURES 5 and 6. At this time, the lower end 61 of each arcing contact 22 is restrained from any further clockwise movement by stop pin 41. The current path at this instant is shown by phantom line 62 in FIGURE 5. The loop portion 63 of current path 62 generates a blow-open effect between bridge 19 and arcing contacts 22 causing bridge 19 to move more rapidly in the clockwise direction. Current loop 63 further serves to urge an are which may be drawn between arcing 22 and butt 24 contacts in an upward direction towards an arc chute which may be operatively connected to circuit breaker The blow-open current loop 63 thus causes more rapid extinguishment of an arc. As can be seen from FIGURE 5, there are two current loops, namely the current loops 54 and 63. The current loop 54 is formed in such a manner as to urge the contact 22 to move still further in the clockwise direction. Thus, this current loop assists in the movement of the bridge 19 toward the fully open position. The current loop 54 is restrained from affecting the circuit breaker operation after the lower end 61 of contact structure 22 bears against the pin 41. Once this happens, the predominant current loop is the current loop 63 which, as described above, aids in the opening movement of bridge 19 and urges a current are formed between the contacts as they separate in the upward direction for extinguishment thereof.

Bridge 19 is moved still further in a clockwise direction until it assumes the position shown in FIGURE 6, at which time the movement of bridge 19 is halted. Piston 65 which is movably mounted in cylinder 70, has a tubular extension 65a which is connected to one end of cradle member 66 by pivot 67. The other end of cradle member 66 is connected to bridge 19 by pivot 68. Piston 65 acts as a cushioning means to slow down the movement of bridge 19 as it nears the fully opened position shown in FIGURE 6. The air which is compressed within cylinder 70, as piston rod 65w moves to the right, is directed between arcing 22 and butt 24 contacts by means of nozzle 69 so that the air compressed in cylinder 70 will exit through nozzle 69 to blow the are drawn between contacts 22 and 24 upward into an associated arc chute. This air blast will greatly aid in the extinguishing of the arc. Another means by which the compressed air in cylinder 70 may be fed into the area of contacts 22 and 24 is disclosed in United States Patent No. 2,775,670, issued December 25, 1956' to W. C. Geiger, In, entitled Combined Air Pufiter Air Buffer for Circuits Breakers and assigned to the assignee of the instant application and this patent is hereby incorporated into the instant application. Strap 71 which is connected to lower disconnect device 16 at pivot 72 and are runner 73 (shown by the dotted line of 6 FIGURE 4) at pivot 74, provides the current path between arc runner 73 and disconnect device 16 when an arc is drawn between the runners of an associated arc chute (not shown).

The closing operation of circuit breaker 10 is as follows: After a fault condition has been cleared, push rod moves in the direction of arrow 81 in FIGURE 6, thereby urging bridge 19 in a counter-clockwise direction around pivot 2t). When bridge 19 reaches the position shown in FIGURE 5, arcing contacts 22 are engaged by butt contacts 24. At the instant contacts 22 and 24, touch, current begins to flow in the path 62 shown in FIG- URE 5. Blow-on current loop 54, aided by spring 37, urges each arcing contact 22 into firmer engagement with its cooperating butt contact 24.

When the closing operation reaches the position shown in FIGURE 5, it can be seen that the two current loops 54 and 63 are formed at this time. The current loop 63 acts as a blow-open current loop detracting from the closing operation. However, the closing mechanism (not shown) is of such a nature as to substantially minimize any blow-open effect caused by the blow open loop 63.

The current loop 54, on the other hand, is of such a nature as to urge contact 22 in the clockwise direction about its pivot 26, thereby assisting spring means 37 in maintaining rm engagement between contacts 22 and 24 during the closing operation. This assistance will be maintained so long as the current path therethrough is maintained, with the circuit breaker in the fully closed position.

It should be noted that arcing contacts 22 and butt contacts 24 in being the first to close, bear the initial current surge upon closing, thus keeping any harmful effects, such as pitting, from occurring on the contact surfaces of main 21 and butts 23 contacts. A bridge 19 moves further in p the counter-clockwise direction, butt contacts 23 touch upon main contacts 21.

At that instant, a second current path (as shown in FIGURE 2) is established. Loop 51 of current path 50 generates a blow-closed effect which cooperates wit-h springs 29 to urge main contacts 21 into firmer engagement with butt contacts 23. Bridge 19 halts its counterclockwise movement when it reaches the position shown in FIGURE 3. Piston also serves as a cushioning means in the closing operation by absorbing some of the energy imparted to bridge 19 during its counter-clockwise rotation. This cushioning effect protects the elements mounted upon conductive head 40 from a severe impact.

It should be noted that during both the closing and tripping operations, there is a wiping action between arcing 22 and butt 24 contacts and main 21 and butt 23 contacts. The wiping action removes any oxide deposits on the surfaces of the contacts minimizing contact resistance.

FIGURE 7 is a cross-sectional view taken along line 7-7 of FIGURE 6 showing the construction of pivot 26. Arcing contacts 22 are rigidly mounted to cylinder 77. Arcing contacts 22 are positioned between side plates 25 and mounted thereto by bolt or rod and nut 78. Inserted within cylinder 77 and surrounding bolt 75 is a spring 76. Spring 76 presses against right-hand side plate 25 .at one end and notch 79 at the other end, thus placing cylinder 77 electrical engagement with bolt 75. This pivot assembly serves to insulate arcing contacts 22 from side plates 25 except at the engagement thereof with cylinder 77 and nut 78. This construction preserves the current loop 54 (shown in FIGURE 3) formed between side plates 25 and arcing contacts 22 which in-turn, creates the blow-on effect of current loop 54. Pivot 20 which connects bridge 19 to disconnect device 16 is of similar construction.

Referring now to FIGURES 8 and 9 conductive head 102 is connected to upper terminal of terminals 99. Arms 102a (only one of which is shown) extend outward from head 102. Arcing contact is pivotally mounted by pin 101 which extends through an aperture 101a in arcing contact 100 and apertures 101a in each arm 102a. Side plates 124 (only a portion of one is shown) are mounted to conducting head in a manner similar to that shown in FIGURES 1 and 3. Main contact 103 is pivotally mounted to semi-circular portion 10217 of conductive head 102. It should be noted that a greater contact surface exists between conductive head 102 and main contact 103 at point 106 than exists at point 107. This causes current flowing through the circuit breaker to assume the path shown by phantom line 121 thereby creating a blow-on loop 125 to urge main contact 105 into rigid engagement with cooperating main contact 10511 when the contact structure is in the position shown in FIGURE 8.

Portion 112 of main contact 103 extends through an aperture 111 in plate 140. The edges 113 and 113a of aperture 111 in cooperation with portion 112 serve to limit the movement of main contact 103. Springs 116 and 117 urge main 103 and arcing 100 contacts respectively into engagement With the cooperating contacts of 105a and 104a when the contact structure is in the engaged or closed position.

Edge 108 of arcing contact 100 abuts surface 103:: when the contact structure is in the open position shown in FIGURE 9, edge 103a serving to limit the clockwise movement of arcing contact 100 during the tripping operation.

The upper end of arcing contact 100 extends to the left and has a highly conductive plate 109 mounted thereon, plate 109 also being in electrical contact with contact surface 104.

The operation of the alternative contact structure of FIGURES 8 and 9 is as follows: when contact structure 98 is tripped in response to a fault condition, main contacts 105 and 105a disengage prior arcing contacts 104 and 104a channeling all the fault current through the arcing contacts. As contacts 104 and 104a start to disengage an are A (see FIGURE 9) is drawn therebetween. The blow open path A formed between contacts 104 104a coupled with the heat generated by the arc causes the arc to move upward along plate 109 causing the arc to take position B. The current path at this instant is contact 104a, arc B to contact surface 109 arcing contact 100 and conductive head 102. The current path is shown by phantom line 120. It is noted that are B and current path 120 form a current loop C which generates a magnetic field urging arc B in the direction shown by arrow 122. This force acts to more rapidly urge arc B into jump gap 125 thence to rear arc runner 126 resulting in more rapid arc transfer from arcing contact 104 to are runner 126.

Thus it can be seen from the preceding description that we have provided a circuit breaker with fewer moving parts to ensure rapid and reliable operation. Operating bridge 19 is of light weight construction and has no moving parts mounted thereto permitting operating bridge to move at a more rapid speed than prior devices known in the field. Also we have provided blow-closed current loops which ensure firm contact engagement during normal operation and a blow-open current path which does not become effective until the tripping operation.

In the foregoing, we have described our invention only in connection with preferred embodiments thereof. Many variations and modifications of the principles of our invention within the scope of the description herein are obvious. Accordingly we prefer to be bound not by the specific disclosure herein but only by the appending claims.

We claim:

1. In combination, first and second contact pairs, first and second terminals each having first and second ends, a conductive bridge having first and second ends, said conductive bridge being pivotally mounted at its first end thereof to the first end of said first terminal to permit said bridge to be rotated between an open and a closed position, said first contact pair being fixedly mounted a spaced distance apart at the second end of said bridge,

said second contact pair being pivotally mounted a spaced distance apart on said second terminal, said first and second contact pairs being engaged when said bridge is in said closed position and being disengaged when said bridge is in said open position, said first contact being comprised of first and second contact members, said sec ond contact pair being comprised of third and fourth contact members, said fourth contact member having first and second ends, said second terminal, said fourth contact member and said second contact member defining a loop current path to bias said fourth contact member into engagement with said second contact member, said second terminal including a pair of side plates, each of said side plates having an aperture, said first end of said fourth contact member having a cylindrical hole, a cylinder inserted through said hole, the ends of said cylinder engaging said side plates at said apertures, a spring means positioned within said cylinder for urging said contact member into electrical engagement with one of said side plates, said fourth contact member being freely rotatable between a first and second position on said cylinder.

2. In combination, first and second contact pairs, first and second terminals each having first and second ends, a conductive bridge having first and second ends, said conductive bridge being pivotally mounted at its first end thereof to the first end of said first terminal to permit said bridge to be rotated between an open and a closed position, said first contact pair being fixedly mounted a spaced distance apart at the second end of said bridge, said second contact pair being pivotally mounted a spaced distance apart on said second terminal, said first and said second contact pairs being engaged when said bridge is in said closed position and being disengaged when said bridge is in said open position, said first contact pair being comprised of first and second contact members, said second contact pair being comprised of third and fourth contact members, said fourth contact member having first and second ends, said second terminal, said fourth contact member and said second contact member defining a loop current path to bias said fourth contact member into engagement with said second contact member, said second terminal including a pair of side plates, each of said side plates having an aperture, said first end of said fourth contact members having a cylindrical hole, a rod inserted through said hole, the ends of said rod engaging said side plates at said apertures, a spring means positioned within said cylindrical hole surrounding said rod for unging said fourth contact member into electrical engagement with one of said side plates, said fourth contact member being freely rotatable between a first and second position on said rod, each of said side plates having an elongated notch adjacent to its said aperture, said notch forming an acute angle between a first line bisecting said notch and a second line drawn between the ends of said fourth contact member when said bridge is in its closed position.

3. In combination, first and second contact pairs, first and second terminals each having first and second ends, a conductive bridge having first and second ends, said conductive bridge being pivotally mounted at its first end thereof to the first end of said first terminal to permit said bridge to be rotated between an open and a closed position, said first contact pair being fixedly mounted a spaced distance apart at the second end of said bridge, said second contact pair being pivotally mounted a spaced distance apart on said second terminal, said first and said second contact pairs being engaged when said bridge is in said closed position and being disengaged when said bridge is in said open position, said first contact pair being comprised of first and second contact members, said second contact pair being comprised of third and fourth contact members, said third contact member having a generally L-shaped configuration, said third contact member having a first and second end, said second terminal including a conductive head having a groove, said first end 9 of said third contact member being located within said groove, said second end of said third contact member engaging said first contact member when said bridge is in its closed position, said third contact member being rotatable between a first and second position, said first end of said third contact member being pivotally rotatable within said groove, said second terminal further including mechanical bias means for urging said third contact mem her into engagement with said first contact member, said conducting head and said third contact member forming a loop current path for urging said second end of said third contact member into engagement with said first contact member svhen current flows therethrough, said second terminal further including a stop pin to restrain movement of said third contact member beyond its said second position, said fourth contact member being positioned adjacent said stop pin, said stop pin restraining movement of said fourth contact member at a time after it restrains'the movement of said third contact member.

4. In combination, first and second contact pairs, first and second terminals each having first and second ends, a conductive bridge having first and sec-ond ends, said conductive bridge being pivotally mounted at its first end thereof to the first end of said first terminal to permit said bridge to be rotated between an open and a closed position, said first contact pair being fixedly mounted a spaced distance apart at the second end of said bridge, said second contact pair being pivotally mounted a spaced distance apart on said second terminal, said first and said second contact pairs being engaged when said bridge is in said closed position and being disengaged when said bridge is in said open position, said first contact pair being comprised of first and second contact members, said second contact pair being comprised of third and fourth contact members, said third contact member having a generally L-shaped configuration, said third contact member having a first and second end, said second terminal including a conductive head having a groove, said first end of said third contact member being located within said groove, said second end of said third contact member engaging said first contact member when said bridge is in said closed position, said third contact member being rotatable between a first and second position, said first end of said third cont-act member being pivotally rotatable within said groove, said second terminal further including first mechanical bias means for urging said third contact member int-o engagement with said first contact member, said conducting head and said third contact member forming a loop current path for urging said second end of said third contact member into engagement with said first contact member when current flows therethr-ough, said second terminal further including a stop pin to restrain movement of said third contact member beyond its said second position, said fourth contact member being positioned adjacent said stop pin, said stop pin restraining movement of said fourth contact member at a time after it restrains the movement of said third contact member, said second terminal including second mechanical bias means for urging said fourth contact member into engagement with said second contact member, said fourth contact member being rotatable between a first and second position, said stop pin restraining the movement of said fourth contact member beyond its said second position, said third contact member being disengaged from said first contact member before said fourth contact member becomes disengaged from said second contact member when said conductive bridge moves from its closed position to its open position, said third contact member rotating in a first direction and said fourth contact member rotating in a second direction opposite said first direction when said conductive bridge is moved from its closed to its open position.

5. In combination, first and second contact pairs, first and second terminals each having first and second ends, a conductive bridge having first and second ends, said conductive bridge being pivotally mounted at its first end thereof to the first end of said first terminal to permit said bridge to be rotated between an open and closed position, said first contact pair being fixedly mounted a spaced distance apart at the second end of said, bridge, said second contact pair being pivotally mounted a spaced distance apart on said second terminal, said first contact pair being engaged by said second contact pair when said bridge is in said closed position and being disengaged when said bridge is in said open position, said first contact pair being comprised of first and second contact members, said second contact pair being comprised of third and fourth contact members, said first and third contact members engaging one another when said bridge is in its closed position, said second and fourth contact members engaging one another when said bridge is in its closed position, said second contact member, said fourth contact member, and said second terminal defining a loop current path to bias said fourth contact member into engagement with said second contact member, said fourth contact member having first and second ends, said second terminal including :a pair of side plates, each of said side plates having an aperture, said fourth contact member having a cylindrical hole theret'hrou-gh, a rod having first and sec-ond ends inserted through said hole, said first and second ends of said rod engaging the aperture in each of said side plates respectively, spring means positioned within said cylindrical hole and surrounding said rod for urging said fourth con-tact member into electrical engagement with one of said side plates, said fourth contact member being freely rotatable in a first direction between a first and second position on said rod, each of said side plates having an elongated notch adjacent said aperture, said notch being positioned to form an acute angle between a first line bisecting said notch and a second line drawn between the ends of said fourth contact member when said bridge is in its closed position, a stop pin connected between said side plates for restraining said fourth contact member from moving beyond its said second position when said bridge is in its open position, said third contact member being rotatable between a first and sec-ond position in a second direction opposite said first direction, said third contact member being positioned adjacent said stop pin, said stop pin additionally restraining the movement of said third contact member beyond its said second position when said bridge is moved from its closed toward its open position.

6. For use in cooperation with an associated arc chute, a circuit interrupter comprising in combination, first and (second contact pairs, first and second terminals each having first and second ends, a conductive bridge having first and second ends, said conductive bridge being pivotallv mounted at its first end thereof to the first end of said first terminal to permit said bridge to be rotated between an open and a closed position, said first contact pair being comprised of first and second contact members fixedly mounted a spaced distance apart at the second end of said bridge, said second terminal including a conductive head, said second contact pair comprising third and fourth rotating contact members movable relative to said conductive head and rotatable in opposite direct-ions relative to one another between first and second positions, said second terminal further including a pair of side plates mounted on opposite sides of said conductive head, pivot means connected between said side plates and through said fourth rotating contact member to position said fourth rotating contact member for engagement with said second contact member when said bridge is in said closed position, said pivot means including spring means for establishing a conductive path between one of said side plates and said fourth rotating contact member, mechanical bias means positioned between said conductive head and said fourth rotating contact member for urging said fourth rotating contact member into engagement with said second contact member, said side plates each having an elongated notch for establishing a loop current path between said one side plate and said fourth contact member for urg- 11 ing said fourth contact member into engagement with said second contact member when current flows therethrough, said third rotating contact member having a generally L- shaped configuration, said third contact member having first and second ends, said conductive head having a groove for insertion of said first end of said third contact member, said third contact member pivoting about said first end, said conductive head and said third contact member forming a loop current path for urging the second end of said third contact member into engagement with said first contact member when current flows therethrough, a stop pin mounted between said side plates, said stop pin being positioned to restrain rotation of said third and fourth contact members beyond their said second positions when said bridge is moving from its closed position toward its said open position, said third contact member and said first contact member disengaging prior to disengagement of said fourth and second contact members when said bridge is moving from its closed position to its said open position, said second contact member, said fourth contact member and said second terminal forming :a loop current path whereby current flowing thereth-rough urges said contacts towards disengagement and an are which is drawn therebetween is urged in the direction of an associated arc chute.

References Cited by the Examiner UNITED STATES PATENTS KATHLEEN H. CLAFFY, Primary Examiner.

MAX L. LEVEY, ROBERT K. SCHAEFER, BERNARD A. GILHEANY, Examiners. 

1. IN COMBINATION, FIRSTA AND SECOND CONTACT PAIRS, FIRST AND SECOND TERMINALS EACH HAVING FIRST AND SECOND ENDS, A CONDUCTIVE BRIDGE HAVING FIRST AND SECOND ENDS, SAID CONDUCTIVE BRIDGE BEING PIVOTALLY MOUNTED AT ITS FIRST END THEREOF TO THE FIRST END OF SAID FIRST TERMINAL TO PERMIT SAID BRIDGE TO BE ROTATED BETWEEN AN OPEN AND A CLOSED POSITION, SAID FIRST CONTACT PAIR BEING FIXEDLY MOUNTED A SPACED DISTANCE APART AT THE SECOND END OF SAID BRIDGE, SAID SECOND CONTACT PAIR BEING PIVOTALLY MOUNTED A SPACED DISTANCE APART ON SAID SECOND TERMINAL, SAID FIRST AND SECOND CONTACT PAIRS BEING ENGAGED WHEN SAID BRIDGE IS IN SAID CLOSED POSITION AND BEING DISENGAGED WHEN SAID BRIDGE IS IN SAID OPEN POSITION, SAID FIRST CONTACT BEING COMPRISED OF FIRST AND SECOND CONTACT MEMBERS, SAID SECOND CONTACT PAIR BEING COMPRISED OF THIRD AND FOURTH CONTACT MEMBERS, SAID FOURTH CONTACT MEMBER HAVING FIRST AND SECOND ENDS, SAID SECOND TERMINAL, SAID FOURTH CONTACT MEMBER AND SAID SECOND CONTACT MEMBER DEFINING A LOOP CURRENT PATH TO BIAS SAID FOURTH CONTACT MEMBER INTO ENGAGEMENT WITH SAID SECOND CONTACT MEMBER, SAID SECOND TERMINAL INCLUDING A PAIR OF SIDE PLATES, EACH OF SAID SIDE PLATES HAVING AN APERTURE, SAID FIRST END OF SAID FOURTH CONTACT MEMBER HAVING A CYLINDRICAL HOLE, A CYLINDER INERTED THROUGH SAID HOLE, THE ENDS OF SAID CYLINDER ENGAGING SAID SIDE PLATES AT SAID APERTURES, A SPRING MEANS POSITIONED WITHIN SAID CYLINDER FOR URGING SAID CONTACT MEMBER INTO ELECTRICAL ENGAGEMENT WITH ONE OF SAID SIDE PLATES, SAID FOURTH CONTACT MEMBER BEING FREELY ROTATABLE BETWEEN A FIRST AND SECOND POSITION ON SAID CYLINDER. 